The present invention relates to a fuse unit to be used mainly for, for example, an electric circuit for an automobile, and relates particularly to a fuse unit in which a bus bar and a resin covering body are integrated by insert molding, and a method of manufacturing the fuse unit.
In the prior art, fuse units have been used to protect an electric circuit mounted in an automobile or the like and various electric components connected to the electric circuit. Specifically, when an unintended overcurrent flows in the electric circuit, a fusing portion fuses due to heat generated by overcurrent to protect the various electric components so as not to allow excess current to flow through the electric components.
There are various kinds of fuse units depending on the application, and, for example, the fuse unit described in Patent Literature 1 is used for connecting an on-board battery and electric wires supplying power to various electric components. In such an on-board fuse unit, there is a possibility that a bus bar is damaged by vibration of a vehicle body. Thus, a resin is poured and insert-molded in a state where the bus bar is disposed in a molding die, whereby the bus bar and a resin covering body are integrated to avoid damage of the bus bar due to vibration.
The fuse unit may be provided with a tuning fork terminal used for attaching an arbitrary fuse from the outside. Specifically, as shown in a bus bar 700 in FIGS. 6(a) and 6(b), the bus bar 700 is constituted of a battery terminal plate 710, a connection side terminal plate 720, and a fuse connection terminal 730 constituted of a pair of tuning fork terminals, and a fuse is inserted into and attached to the fuse connection terminal 730 from the outside.
Here, a method of manufacturing a fuse unit 800 including the bus bar 700 will be described. First, the battery terminal plate 710 and the connection side terminal plate 720 which are in a state of being connected and integrated with each other, as shown in FIGS. 6(a) and 6(b), are arranged on a fixed side mold plate (not shown). Then, an output side tuning fork terminal 732 is disposed on the fixed side mold plate so as to face an input side tuning fork terminal 731 extending from the battery terminal plate 710. In this state, a movable side mold plate is mated with the fixed side mold plate from the upper side of the fixed side mold plate, and a cavity is formed. Then, when a resin is injected into the cavity, the fuse unit 800, as shown in FIG. 7, in which the bus bar 700 and a resin covering body 810 are integrated is completed.
As shown in FIG. 7, a distal end side of the fuse connection terminal 730 is exposed to outside of the resin covering body 810, and a plate-like blade-type fuse can be inserted into and attached to the distal end of the fuse connection terminal 730. Specifically, an insertion groove is formed in a central portion of each of the input side tuning fork terminal 731 and the output side tuning fork terminal 732, so that metal terminals on both sides of the blade-type fuse are inserted into the respective insertion grooves.
However, in order to insert and attach the blade-type fuse into and to the fuse connection terminal 730, the input side tuning fork terminal 731 and the output side tuning fork terminal 732 are required to be precisely aligned so as to face each other, and if the input side tuning fork terminal 731 and the output side tuning fork terminal 732 are slightly misaligned, it becomes difficult to insert the blade-type fuse. Accordingly, the operation of placing the output side tuning fork terminal 732 on the fixed side mold plate and aligning the position requires a high degree of accuracy, and a manufacturing work of the fuse unit is very troublesome. In addition, at the time of insert molding, it is necessary to prepare the output side tuning fork terminal 732 which is a separate part and to dispose the output side tuning fork terminal 732 on the mold plate, so that the number of components of the bus bar necessary for insert molding is increased corresponding to the output side tuning fork terminal 732.